Image forming apparatus and image forming method

Abstract

A light source emits a light beam for forming an electrostatic latent image on a plurality of image carriers charged by a charging unit. A polygon mirror deflects the light beam from the light source in a main scanning direction. A developing unit develops the electrostatic latent image formed on the image carriers with a developer to obtain a visible image. A fixing unit fixes the visible image transferred onto the recording medium by a transfer unit. The polygon mirror includes four reflection planes with different tilt angles with respect to a rotation axis of the polygon mirror. The control unit includes a correction unit that performs an fθ correction.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application claims priority to and incorporates by reference the entire contents of Japanese priority document 2007-121893 filed in Japan on May 2, 2007.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to an image forming apparatus for forming a color image using an electrophotographic technology, and more particularly, to an image forming apparatus for forming an image through raster scanning using a polygon mirror that includes reflection planes having various tilt angles.[0004]2. Description of the Related Art[0005]Most of conventional color electrophotographic apparatuses including a plurality of photosensitive elements have a tandem structure as shown in FIGS. 8 and 9. In the tandem structure, each images of black (K), yellow (Y), magenta (M), and cyan (C) is formed on an intermediate transfer belt. Therefore, a light source is required for each of the four colors, i.e., at lea...

AI Technical Summary

Benefits of technology

The present invention provides an image forming apparatus and method that can improve the quality of images formed using a light beam and a polygon mirror. The apparatus includes a control unit that performs an fθ correction to ensure accurate and synchronized movement of the light beam. The method includes charging the image carriers, deflecting the light beam with the polygon mirror, performing the fθ correction, forming an electrostatic latent image, developing the image with a developer, transferring the image onto a recording medium, and fixing the image on the recording medium. The technical effects of the invention include improved image quality, reduced image blurring, and improved image stability.

Problems solved by technology

However, a reflection angle of each of the reflection planes is required to be corrected because the reflection angles may be unequal due to production tolerance or the like.

The fθ lens is basically an expensive element.

Although low-cost plastic fθ lenses are available, the plastic fθ lenses are inferior in temperature characteristics or optical characteristics.

However, if the writing frequency increases, the consumption current also increases, which increases an unnecessary radiation and therefore increases costs.

Moreover, if the polygon mirror including reflection planes having two or four types of tilt angles is used, two or four fθ correction lenses are required, which complicates the configuration and increases the costs.

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